"It’s a real possibility that the Democrats may actually nominate
a socialist," the fundraising letter said. "Self-proclaimed
socialist Bernie Sanders is catching fire in the Democrat
primary. He's smashing online fundraisng [sic] records and has
even reported over two million online donations."

It continued: "We have to stop this! Pitch in today to keep
America free from socialism."

The fundraising pitch comes as Sanders, a self-avowed
democratic socialist, has attempted to quell concern among some
Democrats. Those Democrats, many of whom support Democratic rival
Hillary Clinton, have expressed fear that being on the same
ticket as Sanders could alienate more moderate voters in
swing states and districts.

Sanders has aggressively countered the impression that his
nomination would not bode well for Democrats in a general
election, pointing out that he performs well in theoretical
head-to-head matchups with some Republican presidential
candidates.

On Sunday, Sanders said the enthusiasm he's generated behind his
insurgent candidacy will motivate irregular and first-time voters
to participate, which he asserted will propel him and
other Democrats to victory.

"Because I think our campaign is the campaign that is generating
excitement and energy that will result in a high voter turnout.
Republicans win when voter turnout is low. Democrats win when
voter turnout is high," he continued. "I think our campaign is
raising issue about a rigged economy, a corrupt campaign-finance
system."

Clinton on Sunday suggested she agreed with lawmakers like
Sen. Claire McCaskill (D-Missouri), who has said that Republicans "can't wait to
run an ad with a hammer and sickle" against Sanders.

"That certainly is what a lot of Democratic leaders are saying,
and I take them at their word," Clinton said when asked about
concerns about how Sanders would affect Democrats down the
ballot.

"They know their states. They know the country. They know we have
to take back the Senate," she continued. "They want to make some
advances in the House as well as at governor and legislature
levels across the country."

Republicans haven't been shy in expressing their enthusiasm about
Sanders' rising popularity among Democratic voters.

During the last Democratic debate,
the Republican National Committee sent out a series
of emails fact-checking Clinton's attacks on
Sanders. Last week, a super PAC founded by a prominent
Republican donor also began running attack ads against
Sanders in Iowa that actually touted traits that
Democratic voters support.